RAF Northolt Islanders

Having moved to RAF Uxbridge recently, it became apparent that the approaches to RAF Northolt were almost directly overhead.

I am familiar with the Islander aircraft from my time in NI. I was just wondering what role they perform here on the mainland UK. (I have heard ELINT/SIGINT?) They have been flying some rather unusual hours lately, late nights and weekends, certainly not your usual 9-5

Thanks;)